A railway signal light is used in a field environment. A train driver must be able to clearly see light emitted from the signal light at a reasonable distance in various weather conditions. Thus, the signal light must be designed to meet related national requirements. Corresponding standards of the railway signal light are established in China, wherein a horizontal beam angle of light generated by the signal light should be between −2.2° and 6°, a vertical beam angle should be between −1.02° and 6°, and a light spot generated thereby should be uniform.
The current railway signal lights mostly use a halogen lamp as a light source, while it has a high power, and will waste a lot of energies in a long time use. In addition, there is only one halogen lamp as the light source, then, if the halogen lamp is damaged and is not timely changed, the signal light will stop working, so the operation reliability is relatively poor. A signal light taking an LED as a light source is also available in the current market, and the light source of such signal light usually consists of a plurality of LEDs. As there is inevitably a certain spatial distance between the LEDs, light emitted from respective LED of the light source will generate a light point which cannot be well eliminated with a lens of a traditional signal light for obtaining a uniform light spot. However, such light points make it quite difficult for secondary optical design of the signal light.